[syslinux] Chainloading from Vista x64 bootloader to Extlinux?

[Miller, Shao]

Good day Rune,

Regarding your challenge chain-loading to an Ext[2|3]FS partition
containing EXTLINUX from a Vista 64-bit Windows installation's
boot-loader:

Do you happen to know what code is on the MBR?  Is it good ol' standard
MBR code?  Was it installed by Windows?  Was it Syslinux' mbr.bin?  Did
some other OS put code there?  If you search for string in it, what do
you see?

dd if=/dev/sda of=~/sda_mbr.bin count=1
strings ~/sda_mbr.bin

I would expect there to be BCD boot-code installed on the Windows
partition's first sector (often simply called "boot sector").  I was not
aware that BCD boot-code went into the MBR, so this is an interesting
challenge.

If H. Peter muttered something about MS changing the boot protocol, it
might have to do with how the registers are filled upon chain-loading
another partition's boot-sector.  Things like the DL register might be
critical.

Regarding the previous discussion of SYSLINUX.EXE for Windows 64-bit:

I don't think any of that information is relevant to your situation,
Rune.  That discussion concerned installing SYSLINUX from a 64-bit
Windows environment, if I recall correctly.  If you are able to boot
Linux and install EXTLINUX from Linux, then you needn't worry about
installing SYSLINUX from a 64-bit Windows.

- Shao Miller